U. S. Pat. No. 4,708,543 discloses a coarse radially adjustable tool holder employing an eccentric adjustment ring combined with linear guide means confining the tool point to a linear adjustment path within a fine adjustment eccentric bushing such as provided by "Briney Precision Adjustment Tool". Such tool holder accommodates a boring bar capable of operating within relatively small diameters. The tool holder provides a relatively coarse adjustment, e.g., in the order of 0.100" to 0.125" with graduations in a rotating gauge ring equal to 0.005" in diameter with a secondary fine adjustment of 0.010" with a precision of 0.0005" diametrical adjustment for each graduation of adjustment gauge ring.
For each of the coarse and fine adjustments, an eccentric bushing is employed to effect a total range of adjustment based on radial eccentricity.